1. Field of the Invention
An embodiment of this invention relates to a method and apparatus for modifying polarity of light.
2. Discussion of Related Art
Lithographic machines are used in semiconductor processing to expose selected areas of photoresist material to light, so that the photoresist material can the be patterned. Some lithographic machines control the polarity of light to obtain tighter control over the quality of light. However, some lithographic machines do not control the polarity, so that the light is arbitrarily polarized. For example, the light may propagate through a transverse plane, and all the light in respective rectangular or square cells of the transverse plane may be polarized the same, but may be polarized differently from one cell to the next. The optics of such an apparatus can normally be replaced with optics that control polarization, but at great cost.